Single-use mechanical microkeratome offers reliable, safe, effective alternative for sub-Bowman's keratomileusis

June 15, 2009

The One Use-Plus microkeratome (Moria) equipped with the 90-µm head, which cuts an average flap thickness of ~100 µm, is a single-use solution for performing sub-Bowman's keratomileusis. It performs with excellent reproducibility, comparing well with the femtosecond laser, and creates high-quality, planar-like flaps and smooth stromal beds.

Key Points

San Francisco-A single-use mechanical microkeratome (One Use-Plus, Moria) provides an easy-to-use, safe, effective, and economical alternative to the femtosecond laser (IntraLase, Abbott Medical Optics) for performing sub-Bowman's keratomileusis (SBK), said Gustavo Tamayo, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

"There is significant interest in SBK because of the potential benefits of this thin-flap procedure, including better clinical outcomes as well as preservation of biomechanical properties, reduced risk of ectasia, and the ability, perhaps, to treat more patients with thinner corneas and higher levels of myopia," said Dr. Tamayo, Bogota Laser Refractive Institute, Bogota, Colombia.

"With both disposable heads and suction rings, the [microkeratome] fully represents a single-use solution for the refractive surgeon," Dr. Tamayo said. "Available evidence shows it performs reliably in creating thin flaps with a near planar profile and leaving an extremely smooth stromal bed, but it provides these outcomes with a cost that is much lower than femtosecond laser flap creation."

Flap dimensions were measured using intraoperative ultrasonic pachymetry and calipers. Mean flap thickness (range) was similar in the mechanical microkeratome [101 µm (85 to 108 µm)] and femtosecond laser [104 µm (82 to 110 µm)] groups, and the mean flap diameters were identical (9.1 mm) with a very small range of only 0.3 mm in each group.

"However, when using the femtosecond laser, it was necessary to reposition the suction ring in six of 20 eyes in order to maintain the diameter constant," Dr. Tamayo said.

Corneal biomechanical properties measured with a non-contact applanation tonometer (Ocular Response Analyzer, Reichert) showed decreases occurred with use of both the femtosecond laser and the mechanical microkeratome, with slightly more decrease in the mechanical microkeratome group in both corneal hysteresis (5.7% and 10.0%, respectively) and corneal resistance factor (12% and 20.8%, respectively).

Similarly excellent reproducibility in flap dimensions have been achieved with the mechanical microkeratome in other analyses based on Dr. Tamayo's experience in a larger group of eyes and from other investigators who participated in an international, multicenter, prospective study. In Dr. Tamayo's hands, mean ± standard deviation (SD) flap thickness was 109.8 ± 11.9 µm, mean ± SD vertical flap diameter was 9.3 ± 0.14 mm, and mean ± SD hinge size was 3.6 ± 0.4 mm. The mean ± SD horizontal diameter of the stroma available for ablation was 8.9 ± 0.13 mm.

"These bed dimensions are adequate for essentially any planned ablations," he said.

Dr. Tamayo presented anterior segment OCT (Visante, Carl Zeiss Meditec) images from a study by James Lewis, MD, that investigated flap architecture to demonstrate that flaps created using the mechanical microkeratome were nearly planar. Scanning electron microscope images from a cadaver eye study conducted by Richard Duffey, MD, also were shown that highlight the smoothness of the stromal bed after flap creation using the mechanical microkeratome and show the superior quality compared with use of the 60-kHz femtosecond laser for flap creation.

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